The present invention relates to pigments for plastics, glasses, ceramics, paints, enamels, inks and other types of materials, and more particularly relates to the use of alkaline earth-manganese oxide compositions as pigments for use in plastics, paints, coatings, glass enamels and other materials.
Pigments are widely used in various applications such as paints, inks, plastics, rubbers, ceramics, enamels and glasses. There are various reasons for using inorganic pigments. Among these are the coloristic properties of the pigments, their visible as well as ultraviolet (UV) and infrared (IR) reflectance characteristics, their light fastness and their high temperature stability, which is necessary when the objects being colored are formed at elevated temperatures. A summary of many types of inorganic pigments and some of their applications can be found in the Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition, Volume 18.
Manganese is used as a chromophore in several mixed metal oxide pigments, which are listed in the Dry Color Manufacturers Association (DCMA) classifications. In the corrundum structure, manganese is used to form manganese alumina pink corrundum, DCMA number 3-04-5. Manganese is also used as a chromophore in the rutile structure to form brown pigments, such as manganese antimony titanium buff rutile (DCMA 11-20-6), manganese chrome antimony titanium brown rutile (DCMA 11-46-7), and manganese niobium titanium brown rutile (11-47-7). Manganese is also a component in many spinel pigments to form brown or black colors. Examples are manganese ferrite black spinel (DCMA 13-41-9), chrome iron manganese brown spinel (DCMA 13-48-7), and chrome manganese zinc brown spinel (DCMA 13-51-7).
Currently, several of the DCMA classified pigments are used due to their IR reflectance performance. The IR reflective performance is typically determined by the relative amount of reflectance provided in the solar infrared region of the spectrum, i.e., 700 to 2,500 nm in wavelength, compared to the visible region of the spectrum, i.e., 400 to 700 nm in wavelength. Common black pigments such as carbon black have low reflectances in both regions. To obtain enhanced IR reflectance, inorganic black pigments from the classification DCMA 13-50-9, chrome iron nickel black spinel, or DCMA 3-05-3, chrome green black spinel, are used for these applications. The pigment DCMA 13-30-3, cobalt chromite green spinel, also provides a higher IR reflectance than visible reflectance.
The above-mentioned pigments do not provide the desired color values, contain the desired chemistry or provide the desired infrared reflectance properties for many applications. The present invention provides pigments with enhanced color, composition and performance characteristics.
This invention relates to pigments that can be represented by the formula MexMnOy, where Me comprises at least one metal of the alkaline earth metals Ca, Ba, Sr and Mg, x ranges from 0.01 to 99, and y designates the number of oxygen atoms required to maintain electroneutrality. Preferably, x ranges from 0.08 to 12, more preferably from 0.25 to 4, and y ranges from x+1 to x+2. These pigments can be used to color objects, or coat objects by their use in applications such as paints, inks, plastics, glasses, ceramics and the like. The invention also includes the production of these pigments, substitution of other elements into these pigments, and the use of protective coatings on these pigments in order to enhance their properties.
In accordance with an embodiment of the present invention, one property of the alkaline earth-manganese oxide pigments is high infrared reflectance while maintaining a visibly dark color. This high infrared reflectance may result in substantially less heat buildup in colored objects using the present alkaline earth-manganese oxide pigments.
Another property of the present alkaline earth-manganese oxide pigments is their ability to change to a different color when exposed to high temperatures. For example, when surfaces containing these materials are subjected to elevated temperatures by laser marking, legible marks are obtained.
Another aspect of the present invention is to provide a coating composition including a liquid carrier and a pigment comprising alkaline earth-manganese oxide dispersed therein.
Another aspect of the present invention is to provide an article including a substrate matrix and alkaline earth-manganese oxide pigment dispersed in the matrix.
A further aspect of the present invention is to provide an article including a substrate and a coating comprising an alkaline earth-manganese oxide pigment covering at least a portion of the substrate.
Another aspect of the present invention is to provide a method of making an alkaline earth-manganese oxide pigment. One method includes the steps of mixing powders capable of yielding metal oxides, and calcining the mixture.
These and other aspects of the present invention will be more apparent from the following description.